Study On The Key Factors And Improvement Of Flavor Quality Of Yunnan Arabica Coffee

China ranks among the top 15 coffee-producing countries,and the production areas are mainly concentrated in Yunnan and Hainan.Among them,the planting area and green bean production of Yunnan coffee(Coffea arabica L.)account for more than 98%of the national coffee industry.It occupies a pivotal position in China’s coffee industry.Relying on the characteristic plateau climate and rich and diverse ecology,Yunnan coffee is famous all over the world for its unique quality of"thick but not bitter,fragrant but not strong,slightly fruity sour".The Yunnan Provincial Party Committee and the Provincial Government have also designated the coffee industry as one of the eight plateau characteristic agricultural industries.However,the main cultivar of Yunnan coffee is Catimor CIFC7963,which has been popularized for 20 years,the planting area has reached more than 70%,and the problem of rust resistance degradation has also begun to appear.In addition,Yunnan coffee mainly sells raw materials,the end consumer market is not well-known,and the market share is negligible.Therefore,based on the actual production of Yunnan coffee,this study starts from the two key factors of variety and primary processing,and conducts in-depth research on the upcoming variety replacement and the lack of scientific theoretical guidance for coffee intensive processing and explores the processability of green coffee beans.These studies will provide theoretical guidance and technical support for the production of high-quality coffee,and promote the steady and healthy development of Yunnan coffee.The main research content and results are as follows:1.Chemical ingredients characterization of twelve cultivars of Coffea Arabica roasted beansThis work aimed to study the composition differences of roasted beans between 12 coffee cultivars(Catimor 7963,HIBRIDO DE TIMOR,Ruiru 11,Castillo,DTARI 296,DTARI 366,DTARI 392,DTARI 585,SL28,SL34,Catuai-Amarelo and Catuai-Vermelho)from Bourbon-Typica group and Introgressed group under subtropical humid monsoon climate.The water-soluble compounds of roasted coffee beans were characterized by proton nuclear magnetic resonance spectroscopy(~1H NMR),and the aroma components were analyzed by static headspace gas chromatography-mass spectrometry(SHS-GC/MS).In total,20 water-soluble compounds and 43volatile compounds were identified.Both water-soluble and volatile compounds are rich in acidic substances,and the content varied depending on the cultivars.Furthermore,principal component analysis(PCA)clustered 12coffee cultivars into four groups.The four different chemically defined clusters of Arabica cultivars produced by chemical differences cannot reflect the traditional grouping based on introgressed,and it is one-sided to judge coffee quality based on lineage.These results give further insight into the quality characteristics of different coffee cultivars,which is of great significance for guiding the adjustment of cultivars’structure and the breeding of new cultivars.2.Effect of self-induced anaerobic fermentation drying methods on the quality of Yunnan coffee beansIn this study,medium roasted coffee with four different self-induced anaerobic fermentation(SIAF)post-treatments(dry,wet,semi-dry and hot air dry)was used as the material.Chemical profile and sensorial analysis were used to comprehensively analyze the effects of SIAF post-treatments on coffee flavor characteristics from multiple dimensions.A total of 31 water-soluble chemical components and 39 volatile compounds were identified in roasted coffee,and distinct SIAF post-treatments based on chemical orientation make coffee highly differentiated.In addition,the principal component analysis(PCA)of the chemical composition integrated data set showed that the first two principal components could explain 54.9%of the sample variability.All four post-treatments can be classified as"specialty coffees"according to the Specialty Coffee Association(SCA)protocol,with various organoleptic characteristics and flavor attributes.This study was the first to investigate the effect of SIAF combined with different drying method on the quality characteristics of coffee,which is of great significance for stabilizing the quality of Yunnan Arabica coffee and producing specialty coffee with special flavor.3.Effect of anaerobic micro-germination on the quality of commercial Arabica coffee beansThis study aimed to improve the brewing quality of commercial Arabica coffee through anaerobic germination.Changes in important compounds and cupping scores of germination roasting coffee with different germination degrees were investigated by ~1H NMR,HS-SPME-GC-MS,and sensory analysis.Statistical analysis of multivariate analysis results indicated that 6water-soluble chemical components and 8 volatile chemical components have the potential to be markers of germinated roasting coffee.In addition,germination significantly reduced caffeine content and acrylamide formation in roasted coffee.Sensory analysis according to the Specialty Coffee Association(SCA)cupping protocol demonstrated that anaerobic germination modified flavor attributes,improved the quality,and increased sensory scores.Furthermore,anaerobic sprouting increased fruity descriptors,but over-sprouting did not improve overall attributes while producing both fermentative and vegetable descriptors.Therefore,suitable anaerobic germination of green coffee beans can be used as a new strategy to improve the flavor of commercial Arabica coffee.Our research has enriched the processability of green coffee beans.4.Effect of adding sugars combined with anaerobic germination on the quality of commercial Arabica coffee beansThis study aimed to incorporate various flavor precursors(sucrose,glucose,and fructose)into the anaerobic germination treatment of coffee beans to investigate the characteristics of quality changes.Coffee beans were used as raw materials and anaerobic germination was carried out by adding different flavor precursors(5%).The chemical composition and sensory quality changes of each treatment were analyzed.Results showed that the addition of sugars facilitated the harmonization of water-soluble chemical components and the alteration of aroma characteristics in roasted coffee beans.The inclusion of sugars significantly elevated the levels of 5-hydroxymethylfurfural(5-HMF)and volatile aldehydes in roasted coffee.Furthermore,principal component analysis(PCA)performed on a comprehensive chemical composition dataset indicated that the first two major components accounted for 48.7%variability among samples.Sensory analysis based on SCA cupping protocol demonstrated that combining sugars with anaerobic germination transformed coffee flavor properties,enhanced quality,and substantially increased the sensory scores(p<0.05).Compared to added glucose and fructose,sucrose supplementation resulted in the highest sensory score and a more pronounced fruity flavor level.Therefore,the addition of different sugars will change the coffee flavor precursors to form different flavor characteristics,which is conducive to further improving the quality of germination coffee.